A High-Precision Amplitude-Time to Digital Converter based on FPGA for Digital Multichannel Analyzer

摘要: The article presents a high-precision Amplitude-Time to Digital Converter (A-TDC) for using in a Multichannel Analyzer (MCA). Utilizing this method, the MCA quantifies and statistically analyzes the discharge time of nuclear pulse signals, ultimately obtaining the gamma energy spectrum. The autonomous linear discharge circuit presented in this paper significantly simplifies the components and control logic of conventional discharge circuits. By leveraging the underlying logic of the FPGA's internal carry-chain, a delay chain capable of precise time measurement for both leading and trailing edges has been designed, which results in a substantial reduction in logical resource consumption. The high-resolution TDC designed based on the Xilinx Artix-7 series FPGA has a resolution of 69.4ps, and the average value of time measurement precision is 52.3ps. The linear discharge circuit has an inherent nonlinearity of less than 0.05%, and the overall linearity is better than 0.1%. When used in conjunction with a φ25mm×25mm NaI(Tl) detector for measuring the 662 keV full-energy peak of a 137Cs source, the energy resolution achieved is 8.5%.